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KMID : 0376219830200020277
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Chonnam Medical Journal
1983 Volume.20 No. 2 p.277 ~ p.286
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Reflex Action of the Semicircular Canals on Semispinalis and Splenius Capitis Muscles in the Rabbits
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Abstract
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This experiment was conducted to explore the reflex reactions of the neck extensor muscles to excitation of the each semicircular canal in the rabbits. In urethane anesthetized animals, each canal nerve was separately stimulated with a monopolar electrode inserted into the ampulla of the relevant canal, and reflex reactions of the semispinalis and splenius capitis muscles were recorded in terms of changes in isometric tension and electromyographic activity. The following results were obtained.
1. Stimulation of the contralateral posterior canal nerve caused contraction of the semispinalis capitis muscle; isometric tension as well as electromyographic activity of the muscle was increased stepwisely upon graded augmentation of the stimulus-intensity.
2. Electromyographic activity of the semispinalis capitis muscle was increased by stimulation of each canal nerve of the contralateral labyrinth.
3. When the nerves of two vertical canals, acting as a functional pair, were stimulated in turn, the bilateral semispinalis capitis muscle reacted in antagonism; the muscle which was ipsilateral to the stimulated canal was depressed, whereas the contralateral one was excited.
4. When the bilateral horizontal canal nerves were stimulated in turn, ipsilateral semispinalis capitis muscle was depressed, whereas the contralateral one was excited.
5. Semispinalis and splenius capitis muscles in the same side of the neck produced synergic reactions to separate stimulation of the bilateral vertical canal nerve.
6. Semispinalis and splenius capitis muscles in the different side of the neck revealed antagonistic reactions to separate stimulation of the bilateral vertical canal nerve.
Based on the above experimental results, a schematic diagram was drawn to show the functional relation between the semicircular canals and the extensor neck muscles. Comparing this diagram to the previous one proposed by Wilson and his associates for cats, some important controversies were noticed; the reflex action of the ipsilateral anterior and contralateral posterior canals on the muscles were found to be contradictory in the two diagrams.
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